Eccentric head hydrocyclone



y 23, 1968 M. D. WOODRUF'F 3,385,437

ECCENTRIC HEAD HYDROCYCLONE Filed April 2, 1965 INVENTOR Mfll/k/C' D.WOODEUFF Jh 1; El BY 7. 13.4mm;

ATTORNEYS United States Patent Ohio Filed Apr. 2, 1965, Ser. No. 444,99814 Claims. (Cl. 209211) This invention relates to the hydrocyclonicseparation of a flowing slurry or the like into accepted and rejectedfractions, and particularly to improvements therein achieving greateroperating efliciency.

The invention has special, though not limited, reference to hydrocycloneseparators, used in paper making processes to separate clean, usablefibrous material from a flowing slurry which, in addition to the usablematerial, contains unwanted heavier particles and dirt. A device of thekind described comprises means defining a separating chamber circular incross section and open at its opposite ends to define outlets for therespective fractions. Through an inlet at the accepts end the flowingslurry is introduced tangentially into the separating chamber in amanner to progress from one end to the other in a swirling helicalmotion. The accepts end is located to receive and guide an inner vortexin which is comprised the accepted fraction, the rejected fractiondischarging through the opposite or rejects end of the separatingchamber. The described accepts and rejects ends of the separatingchamber are considered as providing for overflow and underflow ofrespective slurry portions. These terms, however, do not denote attitudelimitations since the hydrocyclone can be mounted in any position whichis convenient from an installation standpoint, the speed of movement ofthe slurry through the separator making the device operationallyindependent of gravity.

The instant invention has in view the obtaining of a more thorough andprecise separation between the acceptable and rejectable fractions inthe separating chamber by creating a disturbing influence therein. Theeffect thereof is to reduce slurry consistency, particularly adjacent tothe separator wall and to obviate the tendency of unwanted slurryparticles to orbit within the separating chamber in conditions ofequilibrium brought about by counteracting hydraulic and centrifugalforces.

An object of the invention is to present a generally new and simplifiedmethod of achieving more efficient separation in a hydrocyclone.

A further object of the invention is to present a method and apparatusin hydrocyclonic separators wherein means are provided exerting adisturbing influence within the separating chamber.

Still another object of the invention is to achieve objectives as in theforegoing through means inhering in the structure of the separator.

A still further object of the invention is to achieve operatingefliciency as described in a separator especially characterized bysimplicity of construction and by a useful life which is at least equalto that of standard hydrocylonic separators of the prior art.

A further object of the invention is to provide a hydrocyclonicseparator possessing the advantageous structural features, the inherentmeritorious characteristics and the mode of operation herein mentioned.

With the above and other incidental objects in view as will more fullyappear in the specification, the invention intended to be protected byLetters Patent consists of the features of construction, the parts andcombinations thereof, and the mode of operation as hereinafter describedor illustrated in the accompanying drawings, or their equivalents.

Referring to the accompanying drawing wherein is shown one but obviouslynot necessarily the only form of embodiment of the invention,

FIG. 1 is a view in longitudinal section of a hydrocyclonic separator inaccordance with one illustrated embodiment of the invention;

FIG. 2 is a view in cross section, taken substantially along the line 22of FIG. 1;

FIG. 3 is an enlarged detail view of a created ledge in the separator;

FIG. 4 is a view in cross section, taken substantially along theirregular line 4-4 of FIG. 1; and

FIG. 5 is a fragmentary view in longitudinal section showing anotherillustrated form of the invention.

Like parts are indicated by similar characters of reference throughoutthe several views.

In its illustrated embodiment, the invention is disclosed in ahydrocyclone separator as used especially in the pulp and paper industryto enable high standards of paper cleanliness. From a flowing pulpslurry containing not only the light fibrous material desirable forpaper making but also various undesirable materials, the unit operatesto separate the slurry into acceptable and rejectable fractions,directing these to respectively different outlets. According to theobjectives of the separator the highest possible percentage of barkspecks, dirt solids, fibre aggregates, shives and the like is excludedfrom the accepts outlet and directed as a part of the main slurry to therejects outlet. Within this concept the percentage of the pulp slurryreporting to the rejects outlet incorporates minor amounts of usablefibres and hence is desirably low.

A hydrocyclonic separator according to the illustrated embodiment of theinvention comprises a device of unitary construction, as by being madeof a plurality of sections bolted or otherwise secured together. In FIG.1 such a device 10 includes a body section 11 having the shape of atruncated cone, the interior of such body section being hollow to definea separating chamber \12 and the opposite ends of such chamber openingthrough the 'base and apex ends thereof. Further comprised in the device10 is a head section 13 mounted in generally superposed relation to thebase end of section 11. The head section 13 comprises a cylindricalsleeve-like portion 14. Through the cooperation of an internallythreaded nut 15 the cylindrical portion 14 is drawn down to a seat onthe base end of the section 11, the nut 15 reacting against an externalflange 16 on section 1-1 near the base thereof.

The cylindrical portion 14 is formed with a longitudinal through bore17. Received in the outer end of such bore is an expanded head portion18 of a nozzle 19. A flange 2 1 on head portion 18 is drawn to a seat onthe outer end of the cylindrical portion 14 by an internally threadednut 22. The arrangement is one to hold 5 the assembly comprisingcylindrical portion 14 and nozzle 19 in an assembled position relativelyto one another and to the cone section 11. Further comprised in thenozzle 19 is an axial tube portion 23. Inwardly of the head portion 18the tube 23 projects to a transverse plane defined by the juncture ofthe base end of the body section 11 and the inner end of the cylindricalsleeve portion 14. On the other or outer end of the head portion 18 thetube 23 projects as an externally threaded connector 24 by which thedevice 10 is joined to outlet conduit means. The tube 23 is openthroughout its length and occupies a position in bore v17 spaced fromthe wall thereof and defining therewith an annular chamber 25. Thechamber 25 overlies and communicates with the separating chamber 12 andmay be considered a part thereof.

At its outer end the annular chamber 25 is closed by head portion 18 ofthe nozzle 19. Immediately within the back wall of section 13, asdefined by the head portion 18, is an inlet 26 communicating through alaterally projecting boss 27 with the exterior of the device 10, theboss 27 being adapted to be connected in a system to supply thereto apulp slurry under pressure. The arrangement is one to introduce the pulpslurry into the cylindrical sleeve portion 14 tangentially of the wallof bore 17. The continued application of pressure at the inlet causesthe pulp slurry to progress from the head section of the device throughannular chamber into the base end of section -11 and thence throughseparating chamber 12 to the apex end of section 11 in a swirling,helical motion inducing centrifugal forces.

As a result of these forces there is left in the axis of the device anarea of low pressure creating what may be considered to be an innervortex moving contra to the outer vortex, that is in a direction fromthe apex end to the base end. The nozzle 19 serves in this connection asa vortex finder, the inner end of its tube 23 extending to receive theinner vortex and to conduct it out of the separating device, the outerend of the nozzle being adapted, 'as noted, for connection in asuit-able conduit to conduct the materials caught in the inner vortex toa subsequent process step. In accordance with the concept and mode ofoperation of the separator, relatively light and desirable fibres fromthe liquid pulp slurry are gathered up by the inner vortex and conductedout through the head section 13 by way of nozzle 19. This comprises theaccepted fraction, the remainder of the slurry leaving the separatorthrough the apex end of the section 11 as the rejected fraction.

Considering further the flow effects taking place in the separator, thevelocity of flow of the slurry accelerates rapidly and uniformly as itencounters the decreasing diameter of conical body section 11. Thecentrifugal action forcing heavier particles outward toward the wall ofthe separating chamber is greatly multiplied. At the same time, however,a spiraling column, moving in the opposite direction, is formed in thecentral region of the separating chamber, at the axis of which is aliquid free core. In operation, the light desirable pulp particlestransfer from the outer vortex to the inner vortex and are directedthereby to and through the accepts nozzle 19.

The device provides opposed components of flow directed respectivelytoward the base and apex ends of the separator chamber 12. A pressuredifferential from the outer chamber wall toward the center line or axisof the chamber 12 produces a movement of liquid in this direction, thisbeing in conjunction with the downward component of liquid flow. Somedirt particles moving toward the outer wall under centrifugal influencemay find themselves balanced by the involved forces. As a result, theseparticles assume a position of equilibrium and go into a more or lessfixed orbit. Eventually these particles leave their orbits and appear,unpredictably, in the accepts or the rejects fractions. Also, when theslurry is introduced into the cleaner the pulp and dirt begin to move tothe outside of the separator wall. The population of solids adjacent thechamber wall increases. As subsequent dirt particles attempt to join ormove through this population collisions occur. Some dirt particles thusmay not reach the outer wall but instead be caused to intersect theinner vortex and come under the influence of this stream. The increasedconsistency in the region of the separator wall thus has the effect ofrestricting outward motion of dirt particles, allowing some of theseparticles to be drawn into the center vortex along with acceptablematerial. Pulp material is separated or cleaned in stages andimprovements in the efliciency of the hydrocyclone are desirable asreducing the number of required stages, as well as providing clean,conditioned pulp for the paper making process in as facile andeconomical a manner as possible.

In accordance with the instant invention improved efficiency is achievedby creating a controlled turbulence in the slurry flow in the separatingchamber 12 in an area within or beyond the inner end of nozzle 19. Theflow disturbance has the effect of reducing consistency at the separatorwall and of inhibiting orbiting by dirt particles. In achieving thisresult, in the illustrated instance, the bore 17 in cylindrical sleeveportion 14 is formed eccentrically of the sleeve axis.

The annular chamber 25 and the separating chamber 12 proper accordinglyare misaligned. The sleeve 14 is so positioned atop the base end of bodysection 11 as to align a segment of the wall of bore 17 with the wall ofseparating chamber 12. This occurs in the relatively thin wall portionof the sleeve 14 and the transfer of flowing slurry at this locationfrom the annular chamber 25 to the chamber 12 proper is a relativelysmooth and uninterrupted motion. However, the relatively thicker sectionof sleeve 14 under this mounting condition overlaps the engaged part ofthe base end of section 11 in such manner as to define in effect anarcuate, undercut or inverted ledge 28. The location of such ledge is inthe aforementioned transverse plane at the juncture of sleeve portion 14and the base end of conical body section 11. In consequence of thedescribed construction, slurry flowing helically through the annularchamber 25 encounters an abrupt drop-off at the location of ledge 28.The slurry accordingly reaches the underlying wall of chamber 12 with adiffused eccentric action. The result is to produce roiling turbulencein the region of the separator wall beneath nozzle 19. By reason of thehelical motion of the slurry, the region of turbulence is spreadcircumferentially of the separator wall and is projected as a continuingdisturbance longitudinally thereof. This turbulence'disturbs theequilibrium conditions conducive to orbiting of dirt particles andaccordingly inhibits such orbiting tendency. Also, in the turbulent areathe tendency of pulp particles to assume dense, relatively impenetrableformations is inhibited. The consistency towardand in the region of theseparator wall is accordingly restrained from increasing or isrelatively reduced as before described.

While the bore 17 is eccentrically disposed relative to the axis ofconical body section 11, the nozzle 19 is concentric to such axis. Thisis accomplished by forming in the outer end of the cylindrical sleeveportion 14 a counterbore 29 which is concentric with the axis of section11 and which seats therein the head portion 18 of the nozzle 19. Thebore 17 is eccentric troughout its length except for counterbore 29, andinlet 26 is positioned to be diametrically opposed to the portion ofgreater width of the ledge 28. Modifications of these arrangements are,of course, possible, particularly one placing the ledge 28 at any pointalong the length of the bore 17. Further, the arcuate distance of suchledge may be varied or it may in fact be continuous around thecircumference of the base end of section 11. The present arrangement,whereby a portion of the communicating passage between annular chamber25 and separator chamber 12 is comprised of a smooth uninterruptedsurface is deemed desirable since it gives an opportunity for abrasiveparticles in the slurry to escape from beneath the ledge 28 and bedirected along with other rejectable material to the apex outlet. Sandor other grit may become trapped beneath a continuous ledge 28, and, incontinuous rotation under centrifugal force, produce excessive wear onthe separator wall. It is a feature of this invention that the desired,controlled turbulence is produced without means productive of unusual orexcessive wear, the created turbulence being in the main comprised ofliquid movements resulting from transfer of the pulp slurry from theannular chamber 25 to the relatively misaligned separator chamber 12.

Another modification may find the ledge 28, rather than being downturnedor inverted relative to slurry flow, facing upward or toward inlet 26.The results, in

the production of controlled turbulence are like those of theillustrated form. Slurry reaching such ledge has its flow patterndisturbed, tends to be turned back upon itself and proceeds into andthrough the separator chamber with incorporated areas of turbulence.This modification may be achieved, perhaps most imply, by making bore 17larger in diameter than it is at present in such manner that the formedledge is provided by an arcuate portion of the base end of section 11.

In still another modification nozzle 19 and bore 17 may be madeconcentric with one another while section 11 is made ementric to both.This produces, selectively, either an upturned or down turned ledgecorresponding to the ledge 28. The required degree of eccentricity isslight but if necessary more nearly to align the underfiow apex outletwith the overflow nozzle 23 the body section 11 may be caused to assumea slightly tilted position.

The means of the invention has been described as operating to improvethe efficiency of a hydrocyclone by inhibiting particle orbiting thereinand by reducing consistency toward the separator wall. It is possible,however, that other operational factors are involved presently unknown.Thus no attempt is made exhaustively to analyze the effects produced bythe invention in its various forms. It is known that efficiencyimprovements result and it has been the object herein merely to statesome of the likely or probable causes therefor without excluding others.

In terms of rejection rate, by which is meant the percentage of slurrydischarged through the rejects outlet under given conditions ofpressure, stock consistency, temperature and the like, the instantinvention affords distinct and substantial advantages.

As compared to a standard separator the rejection rate is significantlylower at elevated pulp temperatures. It is well established thatheretofore the higher the temperature of pulp in a pulp mill the greaterwill be the rejection rate. In direct test comparisons, it has beenshown that a standard separator has been adversely affected by increasesin pulp temperature, the rejection rate more than tripling undercomparatively modest temperature rises as from 90 F. to 111 F. Aseparator of the instant invention, however, operating under the sameconditions, has its reject rate relatively unaffected by the temperaturerise. Thus, from a practical standpoint, the separator with theeccentric bore in the head has substantial advantages over a standarddevice. It is capable of operating to greater advantage over a widerange of temperatures. Also it is more efiicient. The turbulence createdin the upper part of the separator chamber prevents matting of thefibers as they move down the inner wall of the cone section. Since theconsistency of the layer near the well is lower with the eccentric headcleaner, there are fewer collisions between a dirt particle making itsway to the wall and the fibres which lie therebetween.

Further, increased separating efiiciency is accomplished underconditions of reduced pressure drop, yielding advantages in lower powerconsumption. Thus the kind and degree of turbulence achieved is such asto facilitate movement of liquid to the center vortex without, however,inhibiting access of acceptable solids thereto. As a result a giventhroughput in terms of gallons per minute may be achieved in a separatorof the present invention at relatively low cost in pressure drop, theindicated reduction over the prior art being in excess of twentypercent.

In referring herein to relatively eccentrically disposed cylinder andbody portions it is not intended to exclude constructions in which theeccentricity is obtained by insert means installed in the head section.Thus a separator with concentric head and body portions may be modifiedto perform in accordance with the present invention by mounting in thehead section a crescent shaped insert or the like producing a ledgecorresponding to and functioning as the ledge 28. Such insert device,within concepts previously expressed, may be coextensive in length withthe head section or occupy only a lower or upper part thereof. FIG. 5hereof shows, in partly diagrammatic form, a separator body 31comprising concentric head and cone sections 32 and 33. A crescentshaped segment 34 is installed in the head section 32 in a generallyopposed relation to an inlet 35 and in a manner presenting a ledge 36over which the slurry discharges in a part of the circumference of thehead in passing into the cone section.

Further, it will be understood that the invention is applicable not onlyto separators having cylindrical head and conical body sections, butalso to separators of single configuration. For example a form ofseparator in common use defines throughout its length a single sectionof a cone. The base end thereof serves as the head and may beconstructed in accordance with any of the foregoing examples to achievethe instantly provided ledge. In substance therefore, the inventioncontemplates a fully conical separator, respective sections of which maybe eccentrically offset to produce a fiow disturbing ledge as providedby the present invention.

From the above description it will be apparent that there is thusprovided a device of the character described possessing the particularfeatures of advantage before enumerated as desirable, but whichobviously is susceptible of modifications in its form, proportions,detail con struction and arrangement of parts without departing from theprinciple involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has beendescribed in language more or less specific as to structural features,it is to be understood that the invention is not limited to the specificfeaures shown, but that the means and construction herein disclosedcomprise but one of several modes of putting the invention into efiect,and the invention is therefore claimed in any of its forms ormodifications within the legitimate and valid scope of the appendedclaims.

Having thus described my invention, I claim:

1. A hydrocyclone providing a separating chamber circular in crosssection and open at its opposite ends to define overflow and underfiowoutlets, said chamber having near one end thereof a feed inlettangentially disposed with respect to the separating chamber;characterized in that a portion of said chamber containing said feedinlet is eccentrically disposed relative to the balance of the chamber,said portion presenting a continuously circular interior wall surfaceparallel to the longitudinal axis of said chamber, the remainder of saidchamber containing the feed inlet being generally concentricallydisposed relative to the balance of the chamber, the feed inlet beingformed in and conforming to the curvature of said surface, said surfaceat its juncture with the balance of said chamber providing a ledgesubstantially at right angles to the axis of said chamber.

2. A hydrocyclone according to claim 1, further characterized in thatsaid ledge is inverted for an abrupt drop off from said portion to thesaid balance of the chamber.

3. A hydrocyclone according to claim 1, characterized in that thediameter of said portion of said chamber at its juncture with thebalance of said chamber is less than the diameter of said balance ofsaid chamber at said juncture with said portion being disposed to aligna part of the interior surface thereof with the surface of the balanceof said chamber while the remainder thereof is in oflfset overhangingrelation to the said balance of said chamber.

4. A hydrocyclone providing a separating chamber circular in crosssection and open at its opposite ends to define overflow and underfiowoutlets, said chamber having body and head sections, the latter having afeed inlet tangentially disposed with respect to the separating chamberto introduce separable material into said chamber; characterized in thatsaid head section is eccentric relative to said body section, therebeing formed at the juncture of said sections an arcuate ledge inducingturbulence in the flow of said material, said ledge being in a planesubstantially at right angles to the flow axis and at its opposite endsbeing of minimum width and progressing .to a location of maximum widthat its mid point.

5. A hydrocyclone according to claim 4, further characterized in thatsaid head section is made relatively small in diameter whereby to causesaid ledge to assume an overhanging relation to said body section.

6. A hydrocyclone according to claim 4, further characterized in thatsaid head section is made relatively large in diameter whereby to causesaid ledge to assume a recessed relation to said body section facingsaid inlet.

7. A hydrocyclone according to claim 4, characterized in that opposingportions of the interior surfaces of said head and body sections arealigned to form a continuing, substantially uninterrupted surface over apart of the juncture between said body and head sections, the remainingpart of said juncture being occupied by said ledge, the ends of saidledge merging smoothly with the said first part of said juncture.

8. In a continuously circular hydrocyclonic separator providing aseparator chamber, an overflow nozzle at one end of said chamber fordischarge of accepted material and an underflow opening at the oppositeend of said chamber for discharge of rejected material, said nozzle andsaid opening being disposed for creation of an inner vortex exitingthrough said nozzle, means for introducing a slurry into said chambertangentially of the wall thereof at said one end to progress helicallythrough said chamber toward said underflow opening, means displaced fromsaid slurry introducing means providing that at least a portion of theinterior wall of the separator chamber is offset to create a turbulenceproducing ledge of lateral extent in the line of flow and generally atright angles to the chamber axis, the bore of said chamber to one sideof said ledge having the axis thereof displaced from the axis of thebore of said chamber to the other side of said ledge.

9. A separator according to claim 8, characterized by a crescent shapedinsert device installed in said chamber to provide the described ledge.

10. A hydrocyclonic separator, comprising a body section having theshape of a truncated cone, the interior of said body section beinghollow to define a separating chamber and the opposite ends of saidchamber opening through the base and apex ends of said body section, ahead section seated at its inner end to the base end of said bodysection, said head section having a through longitudinal bore thereindifferent in diameter from the diameter of said separating chamber atsaid base end of said body section, means for securing said head sectionto said body section in a position disposing the axis of saidlongitudinal bore eccentrically of the longitudinal axis of saidseparating chamber, the juncture of said inner end of said head sectionand the base end of said body section defining a generally crescentshaped ledge in a plane substantially at right angles to thelongitudinal axisof said separating chamber, said head section includingtherein an overflow outlet and a feed inlet tangentially disposed withrespect to said longitudinal bore and said body section including at itsapex end an underflow outlet.

11. A separator as in claim 10 characterized by peripheral edge portionsof said longitudinal bore and said separating chamber aligning with oneanother at said juncture beyond the ends of said ledge for smooth flowtransition from said bore to said chamber in a part of said juncture,the part occupied by said ledge providing for flow disturbance.

12. A hydrocyclonic separator according to claim 11, characterized inthat said longitudinal bore is smaller in diameter than the diameter ofsaid separating chamber at the base end of said body section, said ledgeoverhanging said separating chamber to define an abrupt drop off formaterial flowing to said chamber over said ledge.

13. A hydrocyclonic separator according to claim 11, characterized inthat said outer end of the head section is formed with a counterbore theaxis of which is eccentric to the axis of said bore and in the installedposition of said head section aligned with the axis of said separatingchamber, and means closing the outer end of said head section includinga body portion received in said counterbore, and said overflow outletbeing formed in the axis of said body portion.

14. A hydrocyclone providing means defining a separating chambercontinuously circular in cross-section and means at its opposite endsformed to provide openings to define overflow and underflow outlets,said chamber having near one end thereof a feed inlet tangentiallydisposed with respect to the separating chamber, a portion of saidchamber defining means providing a chamber wall portion which iseccentrically offset relative to the axis of said chamber to provide toat least one end thereof an exposed surface forming part of the chamberwall which lies in a plane transverse to the axis of said chamber andprovides in said plane a ledge thereby to disturb the flow down one sideof the chamber wall, the opposite side of said chamber wall beingsubstantially smooth and generally devoid of offset portions.

References Cited UNITED STATES PATENTS 3,313,311 4/1967 Gilson 209-2112,840,240 6/ 1958 Snyder 210-512 940,076 11/ 1909 Seaver 209-1442,731,147 1/1956 Krebs 209-211 2,735,547 2/1956 Vissac 209-211 2,776,0531/ 1957 Krebs 209-211 2,929,501 3/1960 Fenske 209-144 3,098,036 7/ 1963Neumann 209-144 997,171 7/1911 Zehfus 55-426 FOREIGN PATENTS 1,146,3383/1963 Germany.

FRANK W. LUTTER, Primary Examiner.

1. A HYDROCYCLONE PROVIDING A SEPARATING CHAMBER CIRCULAR IN CROSSSECTION AND OPEN AT ITS OPPOSITE ENDS TO DEFINE OVERFLOW AND UNDERFLOWOUTLETS, SAID CHAMBER HAVING NEAR ONE END THEREOF A FEED INLETTANGENTIALLY DISPOSED WITH RESPECT TO THE SEPARATING CHAMBER;CHARACTERIZED IN THAT A PORTION OF SAID CHAMBER CONTAINING SAID FEEDINLET IS ECCENTRICALLY DISPOSED RELATIVE TO THE BALANCE OF THE CHAMBER,SAID PORTION PRESENTING A CONTINUOUSLY CIRCULAR INTERIOR WALL SURFACEPARALLEL TO THE LONGITUDINAL AXIS OF SAID CHAMBER, THE REMAINDER OF SAIDCHAMBER CONTAINING THE FEED INLET BEING GENERALLY CONCENTRICALLYDISPOSED RELATIVE TO THE BALANCE OF THE CHAMBER, THE FEED INLET BEINGFORMED IN AND CONFORMING TO THE CURVATURE OF SAID SURFACE, SAID SURFACEAT ITS JUNCTURE WITH THE BALANCE OF SAID CHAMBER PROVIDING A LEDGESUBSTANTIALLY AT RIGHT ANGLES TO THE AXIS OF SAID CHAMBER.